Decades-Old Canned Salmon Reveals Surprising Signs of Ocean Recovery

Researchers find rising parasite levels in some salmon species, suggesting a healthier marine ecosystem over time.

Apr. 1, 2026 at 8:23am

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Scientists examined decades-old canned salmon and found increasing levels of tiny parasitic worms, known as anisakids, in certain salmon species over a 42-year period. This unexpected discovery suggests that the overall marine food web has strengthened, as these parasites depend on multiple hosts, including marine mammals, to complete their life cycle. The findings provide a unique window into long-term trends in ocean health.

Why it matters

Understanding how marine ecosystems are changing over time is crucial as the climate shifts, but reliable historical data can be hard to come by. This study demonstrates how creative use of unconventional sources, like archived canned seafood, can offer valuable insights into the past state of the ocean and the recovery of key species like seals, sea lions, and orcas.

The details

Researchers at the University of Washington and Yale University examined 178 cans of salmon collected over four decades in the Gulf of Alaska and Bristol Bay. By carefully dissecting the preserved fish, they were able to count the tiny parasitic worms embedded in the flesh. The team found that anisakid levels increased in chum and pink salmon between 1979 and 2021, while remaining steady in coho and sockeye salmon. These parasites require multiple hosts, including marine mammals, to complete their life cycle, so their rising numbers suggest a strengthening of the overall marine food web.

  • The canned salmon samples were collected between 1979 and 2021.
  • The study's findings were published in April 2026.

The players

Natalie Mastick

A postdoctoral researcher at the Peabody Museum of Natural History at Yale University and the lead author of the study.

Chelsea Wood

An associate professor of aquatic and fishery sciences at the University of Washington and the senior author of the study.

Seafood Products Association

A Seattle-based trade group that had preserved the canned salmon samples over many years for quality control.

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What they’re saying

“Everyone assumes that worms in your salmon is a sign that things have gone awry. But the anisakid life cycle integrates many components of the food web. I see their presence as a signal that the fish on your plate came from a healthy ecosystem.”

— Chelsea Wood, Associate Professor of Aquatic and Fishery Sciences, University of Washington

“Anisakids have a complex life cycle that requires many types of hosts. Seeing their numbers rise over time, as we did with pink and chum salmon, indicates that these parasites were able to find all the right hosts and reproduce. That could indicate a stable or recovering ecosystem, with enough of the right hosts for anisakids.”

— Natalie Mastick, Postdoctoral Researcher, Peabody Museum of Natural History, Yale University

What’s next

The researchers plan to expand their analysis to other archived seafood, such as canned sardines, to further explore historical trends in marine ecosystems.

The takeaway

This unexpected discovery of rising parasite levels in some salmon species suggests that the overall marine food web in the Gulf of Alaska and Bristol Bay has strengthened over the past four decades, potentially due to the recovery of key predator species like seals, sea lions, and orcas. The findings demonstrate the value of thinking creatively about unconventional data sources to gain insights into the past state of the ocean.